Ethylene metallocene-catalyzed

Development of a reduced-order model for metallocene-catalyzed ethylene-norbornene copolymerization reaction... 

Advances in Polymer Technology 22, No.3, FaU 2003, p.209-17 BINARY BLENDS OF EVA AND METALLOCENE-CATALYZED ETHYLENE-ALPHA-OLEFIN COPOLYMERS AND THEIR... 

Metallocene catalyzed ethylene copolymers (MCP) (8) Miranol Rhodia Inc. 

It has been reported by Matsugi et al. that PE-fo-PMMA can be synthesized by ATRP techniques with a CuBr and an N,N,N/,N//,N//-pentamethyldiethyl-enetriamine (PMDETA) catalyst system, or with a RuCl2(PPh3)3 and dibuty-lamine catalyst system. They have used terminally hydroxylated PE, produced by the metallocene-catalyzed polymerization of ethylene with allyl alcohol as starting material. The PE macroinitiator was converted to terminally bromi-nated PE by the bromination of obtained PE-OH with bromo-isobutyric bromide (Fig. 11) [67]. 

PE graft copolymers were synthesized from PE-OH by Inoue et al. using ATRP techniques, adopting similar techniques as mentioned above [74]. PE-g-PMMA and Polyclhylcnc-gra/f-poly( -bulyl acrylate) (PE-g-PnBA) were prepared through the combination of metallocene-catalyzed ethylene/10-undecen-l-ol copolymerization and conversion of the copolymer into P E-g-Br, as a macroinitiator, for ATRP. Well-defined graft copolymers, PE-g-PMMA and PE-g-PnBA, were confirmed by analyses of the detached side chains. Resulting PE-g-PMMA worked well as a compatibilizer. 

DOW in Midland, USA, performed metallocene-catalyzed polymerization of ethylene using a homebuilt tube reactor setup with advanced microflow tailored plant peripherals for heating, temperature monitoring, pressure control and dosing via smart valves and injectors. Screening of process conditions was a driver [19]. Also, flexibility with regard to temperature and pressure at low sample consumption was an issue. Quality of the information is another motivation due to the advanced process control and sensing. 

Parikh, D. R. Edmondson, M. S. Smith, B. W. Winter, J. M. Castille, M. J. Magee, J. M. Patel, R. M. Karajala, T. P. Structure and Properties of Single-site Constrained Geometry Ethylene-Propylene-Diene (EPDM) Elastomers. In Metallocene-catalyzed Polymers -Materials, Properties, Processing Markets, Benedikt, G. M., Goodall, B. L., Eds. Plastics Design Library New York, 1998 p 113. 

Metallocene catalysis is an alternative to the traditional Ziegler-Natta vanadium-based catalysis for commercial polyolefin production, e.g. the use of metallocene-catalyzed ethylene alpha-olefin copolymers as viscosity index modifiers for lubricating oil compositions [23]. The catalyst is an activated metallocene transition metal, usually Ti, Zr or Hf, attached to one or two cyclopentadienyl rings and typically activated by methylaluminoxane. Metallocene catalysis achieves more stereo-regularity and also enables incorporation of higher alpha-olefins and/or other monomers into the polymer backbone. In addition, the low catalyst concentration does not require a cleanup step to remove ash. 

Conventional MAO has very low solubility in aliphatic solvents as well as poor storage stability in solution, which considerably limits its utility. Other more soluble and commonly used aluminoxanes are ethylaluminoxane and isobutylaluminoxane, which are synthesized by the partial hydrolysis of triethyl-aluminum (TEA) and triisobutylaluminum (TIBA), respectively. However, these alkylaluminoxanes do not perform as well as MAO in metallocene-mediated olefin polymerization. " It was reported, however, that tetrakis(isooctyl) alumoxane [(i-octyl)2—O—Al-(i-octyl)2], prepared by reaction of Al(i-octyl)3 with 0.5 equiv of water, exhibits remarkable cocatalytic activity, comparable to or even greater than that obtained with MAO, for ethylene polymerization catalyzed by racemic an5a-bis(indenyl)-type zir-conocene dichlorides. Furthermore, commercial modified methylaluminoxanes (MMAO) available from... 

Kinetic data on olefin polymerization by polymer-immobilized zirconocene are scarce. It is generally accepted that homogeneous metallocene catalysts contain uniform active sites however, if they are immobilized on a polymer support, the MWD polymer production becomes broader compared with a homogeneous catalyst [103]. Kinetic analysis of gas-phase ethylene polymerization catalyzed by (CH3)2[Ind]2ZrCl2 bound at a hydroxylated copolymer of styrene with divinylbenzene and previously activated with MAO (0.17 wt.% Zr) has been carried out [104]. The influence of temperature (333 to 353 K), ethylene partial pressure (2 to 6 atm) and MAO level (molar ratio of MAO to zirconium from 2600 to 10,700) were studied. The activity of the catalyst in the gas-phase process changed from 5 to 32 kg PE (g of Zr atm h)It is possible that there are two types of active site. They are stable to temperature and deactivated by the same mechanism. A first-order reaction takes place. The propagation rate constants of two active sites show a similar dependence on temperature. 

In case of the metallocene-catalyzed random copolymer of ethylene and alpha-olefin (POP and POE), incorporating more comonomer along the polymer backbone reduces density and crystallinity and hence, increases flexibility and softness. However, as the density is decreased, the melting point, crystallization peak temperature and heat resistance decrease and cycle times in injection molding increase. These deficiencies have limited the use of POEs in applications where heat resistance, high temperature compression set, and faster cycle times are desired. 

METALLOCENE-CATALYZED ETHYLENE COPOLYMERIZATION WITH 1-OLEFINS... 

Figures 6 and 7 compare the sequence distributions and TREF chromatograms respectively for Ziegler-Natta- and metallocene-catalyzed ethylene-l-hexene copolymerizations. The lack of hlockiness in the metallocene resin in Figure 6 is demonstrated by the low levels of homopolymer triads, whereas intermolecular compositional homogeneity is shown by the narrow peak for the metallocene resin in Figure 7. It should be noted that while the narrow intermolecular distribution of comonomer content is a direct consequence of the single-site nature of the catalyst, the absence of hlockiness is a reflection of the relative magnitudes of the rate constants for insertion for the two monomers and does not speak to catalyst site diversity. The kinetics of insertion will be treated in the following section.

Toyota, A. Mizuno, A. Tsutsui, T. Kaneko, H. Kashiwa, N. Synthesis and characterization of metallocene-catalyzed propylene-ethylene copolymer with end-capped fnnctionahty. Polymer 2002, 43, 6351-6355. 

Bergstrom, C. H. Sperhch, B. R. Ruotoistenmaki, J. Seppala, J. V. Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy. J. Polym. ScL, Part A.- Polym. Chem. 1998, 36, 1633-1638. 

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